Non-Contact Optical Liquid Level Detection for Semiconductor CVD
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Solution Overview
Problem
Existing liquid material supply devices for semiconductor manufacturing face challenges such as contamination, inaccurate measurement, and instability in liquid level detection due to contact with the liquid material, especially when using float-type sensors and gravimeters, and ultrasonic sensors struggle with bubbling and gas atmosphere contamination.
Innovation Solution
A device that uses a carrier gas to introduce and refill liquid material into a filling container with a constant quantity feeder, employing pipes La and Lb to control the liquid level without direct contact, and inert gas supply to prevent overfilling and maintain a stable liquid level, allowing for continuous supply and refilling without stopping the carrier gas flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If float-type sensors or gravimeters are used to detect liquid material residual volume, then measurement capability is provided, but liquid material contamination or sensor contamination occurs
Solution Approach 1:
The patent introduces a non-contact liquid level detection system that uses optical fields as an intermediary to measure liquid level without physical contact. The detection means includes light sources and sensors that detect changes in light transmission or reflection as the liquid level changes, eliminating the need for sensors to contact the liquid material directly while maintaining measurement capability
Solution Approach 2:
The patent replaces mechanical contact-based measurement systems (float-type sensors, gravimeters) with non-contact optical detection systems. This substitution eliminates mechanical contact between sensors and liquid material, preventing contamination while maintaining measurement precision through optical field interactions
2Object-affected harmful factors
If ultrasonic sensors are used for liquid level detection, then non-contact measurement is achieved, but detection accuracy deteriorates due to bubbling and gas atmosphere contamination
Solution Approach 1:
The patent uses optical fields as an intermediary for liquid level detection, where light transmission or reflection changes indicate liquid level position. This optical intermediary is less susceptible to interference from bubbling and gas atmosphere compared to ultrasonic waves, maintaining detection accuracy while preventing sensor contamination
Solution Approach 2:
The patent detects liquid level by monitoring changes in optical parameters (light transmission intensity, reflection angle) rather than relying on ultrasonic wave propagation. This parameter change approach is more stable in environments with bubbling and gas atmosphere, as optical properties are less affected by these conditions than acoustic properties
3Productivity
If liquid material is supplied by bubbling carrier gas through the liquid, then liquid material supply is achieved, but liquid level becomes unstable making accurate detection difficult
Solution Approach 1:
The patent uses optical fields as a stable intermediary to detect liquid level position through the bubbling carrier gas. The optical detection system can penetrate or pass through the gas bubbles to detect the liquid-gas interface, providing stable liquid level measurement even during active bubbling supply operations
Solution Approach 2:
The patent segments the detection function from the supply function, using separate optical detection means positioned to monitor liquid level independently from the carrier gas bubbling process. This segmentation allows the supply system to operate at high productivity while the detection system maintains stable liquid level monitoring unaffected by the bubbling dynamics
4Loss of information
If sensors are provided inside the filling container for direct liquid material detection, then liquid level can be observed, but sensor contamination and liquid material decomposition occur
Solution Approach 1:
The patent positions optical detection means outside the filling container to detect liquid level through the container wall or at the container opening. The optical field acts as an intermediary that can penetrate the container structure without requiring sensor contact with the liquid material, preventing both sensor contamination and material decomposition while maintaining liquid level information acquisition
Solution Approach 2:
The patent replaces direct mechanical sensor insertion into the filling container with non-contact optical detection. This substitution eliminates the physical presence of sensors in the liquid material environment, preventing contamination and decomposition issues while maintaining the ability to observe and detect liquid level information
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables stable and accurate liquid material supply by maintaining a constant liquid level, preventing contamination and overfilling, and ensuring continuous operation without damaging valves and pressure gauges, even with sensitive materials that decompose under pressure fluctuations.
Implementation Method 1
a bubbling container in which bubbling of a carrier gas is performed inside a liquid layer 1a of liquid material
Implementation Method 2
optical attenuation plate 113 installed in standing position on the surface of float 112... the transmitted light volume increases and decreases according to the up and down motion of the optical attenuation plate 113
Implementation Method 3
detecting the liquid level by means of ultrasonic systems measuring the distance from the top of the container to the liquid level detecting the ultrasound wave reflecting on the liquid level
Data Source
AI summary
Disclosed are methods and apparatuses for supplying a liquid and controlling its level inside of a container. In particular, the liquid inside of the container may be a liquid material suitable for use in a chemical vapor deposition process, wherein the liquid is controlled and supplied in a manner which minimizes the introduction of impurities.